Fundamental matrix (linear differential equation)

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Short description: Matrix consisting of linearly independent solutions to a linear differential equation


In mathematics, a fundamental matrix of a system of n homogeneous linear ordinary differential equations [math]\displaystyle{ \dot{\mathbf{x}}(t) = A(t) \mathbf{x}(t) }[/math] is a matrix-valued function [math]\displaystyle{ \Psi(t) }[/math] whose columns are linearly independent solutions of the system.[1] Then every solution to the system can be written as [math]\displaystyle{ \mathbf{x}(t) = \Psi(t) \mathbf{c} }[/math], for some constant vector [math]\displaystyle{ \mathbf{c} }[/math] (written as a column vector of height n).

One can show that a matrix-valued function [math]\displaystyle{ \Psi }[/math] is a fundamental matrix of [math]\displaystyle{ \dot{\mathbf{x}}(t) = A(t) \mathbf{x}(t) }[/math] if and only if [math]\displaystyle{ \dot{\Psi}(t) = A(t) \Psi(t) }[/math] and [math]\displaystyle{ \Psi }[/math] is a non-singular matrix for all [math]\displaystyle{ t }[/math].[2]

Control theory

The fundamental matrix is used to express the state-transition matrix, an essential component in the solution of a system of linear ordinary differential equations.[3]

See also

References

  1. Somasundaram, D. (2001). "Fundamental Matrix and Its Properties". Ordinary Differential Equations: A First Course. Pangbourne: Alpha Science. pp. 233–240. ISBN 1-84265-069-6. https://books.google.com/books?id=PduY2CjJ1zEC&pg=PA233. 
  2. Chi-Tsong Chen (1998). Linear System Theory and Design (3rd ed.). New York: Oxford University Press. ISBN 0-19-511777-8. 
  3. Kirk, Donald E. (1970). Optimal Control Theory. Englewood Cliffs: Prentice-Hall. pp. 19–20. ISBN 0-13-638098-0. https://books.google.com/books?id=onuH0PnZwV4C&pg=PA19.